There have been suggested several sorts of wake-up devices, each of which may be provided in a position adjacent to a driver's seat within a motor vehicle, to wake-up a driver whenever the driver gets sleepy so as to ensure safe driving.
Japanese Utility Model Gazette No.4-15536 discloses a wake-up device for use in a motor vehicle. Such a wake-up device, having a vibration unit into which a car stereo reproducing signal may be fed, forms a sensible stereo apparatus using both the vibration unit and the car stereo signal, thereby sending both a vibration and a sound to a driver.
However, in the above-mentioned wake-up device, since there is only one sound source for use to produce an audio signal for waking up a sleepy driver, the same sound is repeated again and again, as a result a driver will get tired of the repeated dull sound. For this reason, a wake-up function is not as effective as is expected.